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CaMKII can participate in but is not sufficient for the establishment of the membrane block to polyspermy in mouse eggs

Lookup NU author(s): Professor Keith Jones

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Abstract

Fertilization triggers initiation of development and establishment of blocks on the egg coat and plasma membrane to prevent fertilization by multiple sperm (polyspermy). The mechanism(s) by which mammalian eggs establish the membrane block to polyspermy is largely unknown. Ca2+/calmodulin- dependent protein kinase II (CaMKII) appears to be the key regulator of several egg activation events (completion of meiosis, progression to embryonic interphase, recruitment of maternal mRNAs). Since sperm-induced increases in cytosolic Ca2+ play a role in establishment of the membrane block to polyspermy in mouse eggs, we hypothesized that CaMKII was a Ca 2+-dependent effector leading to this change in egg membrane function. To test this hypothesis, we modulated CaMKII activity in two ways: activating eggs parthenogenetically by introducing constitutively active CaMKIIa (CA-CaMKII) into unfertilized eggs, and inhibiting endogenous CaMKII in fertilized eggs with myristoylated autocamtide 2-related inhibitory peptide (myrAIP). We find that eggs treated with myrAIP establish a less effective membrane block to polyspermy than do control eggs, but that CA-CaMKII is not sufficient for membrane block establishment, despite the fact that CA-CaMKII-activated eggs undergo other egg activation events. This suggests that: (I) CaMKII activity contributes to the membrane block, but this not faithfully mimicked by CA-CaMKII and furthermore, other pathways, in addition to those activated by Ca2+ and CaMKII, also participate in membrane block establishment; (2) CA-CaMKII has a range of effects as a parthenogenetic trigger of egg activation (high levels of cell cycle resumption, modest levels of cortical granule exocytosis, and no membrane block establishment). © 2007 Wiley-Liss, Inc.


Publication metadata

Author(s): Gardner AJ, Knott JG, Jones KT, Evans JP

Publication type: Article

Publication status: Published

Journal: Journal of Cellular Physiology

Year: 2007

Volume: 212

Issue: 2

Pages: 275-280

Print publication date: 01/08/2007

ISSN (print): 0021-9541

ISSN (electronic): 1097-4652

Publisher: Wiley-Blackwell

URL: http://dx.doi.org/10.1002/jcp.21046

DOI: 10.1002/jcp.21046

PubMed id: 17455234


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